Published: Thursday, 8-Mar-2007
New findings presented yesterday at a National Autism Association meeting bolster claims that vaccines may play a role in the development of autism spectrum disorders.
David Ayoub, MD presented data suggesting a correlation between mercury- containing vaccines and rates of pervasive developmental disorder (PDD), a form of autism, in Montreal.
The peak rate of one in 87 children diagnosed with PDD occurred following the period of greatest exposure to the mercury- based vaccine preservative thimerosal. A flattening of the rates studied is now emerging as mercury-containing vaccines have been gradually eliminated from the routine schedule.
This new data points out flaws in a 2006 study published in the journal Pediatrics by Eric Fombonne, MD, et al, which found PDD rates continued to increase even when rates of MMR vaccination and use of mercury-containing vaccines decreased. The study population consisted of a single Montreal school board that was an Autism Center of Excellence, suggesting an over- ascertainment of regional diagnoses. Dr. Ayoub and co-authors Monica Ruscitti, BA, and F. Edward Yazbak, MD broadened the data to include all five Montreal school boards.
The earlier study also reported PDD rates in children from Montreal, but MMR coverage data was taken from Quebec City located 265km from Montreal. The researchers confirmed MMR coverage rates actually increased in Montreal along with PDD, noting a sharper rise in rates after the number of required MMR shots doubled.
The Pediatrics paper claimed there was no exposure to mercury from vaccines post-1996 although several mercury-containing vaccines were administered well beyond 1996. "It's irresponsible that such flawed data was published in a medical journal. This new information confirms a relationship between vaccines and autism that can't be explained by better diagnosing or changing diagnostic criteria," said Karen McDonough, NAA -- Chicago president.
Drs. Ayoub and Yazbak detailed the Fombonne study flaws in letters to Pediatrics which the journal declined to publish. Editor Jerold F. Lucey, MD stated in a reply, "I believe the evidence of no link between MMR and Autism is sufficient. It's not worth publishing more on this subject."
"This dismissal of legitimate concerns regarding data affecting those suffering with autism is a disgrace," commented Ms. McDonough.